Tetracyclo nonene

Some of the chemical properties of norbornadiene have been summarized in Fig. 1. The reactions shown will not be discussed explicitly. The chemistry of norbornadiene is characterized by strain and homocon-jugation. Hence the olefin undergoes a series of addition reactions which are frequently accompanied by the formation of the nortricyclene system, the direction of electrophilic attack being usually exo. 20 The diene was found to react with certain vinylogs or dienophiles to produce derivatives of tetracyclo[3.2.1.P .02- ]nonane (VI), or the corresponding nonenes (VII) 23-26 -. 

At higher temperatures (290°C), the 4.2.1 triene gives c/5 -8,9-dihydroindene by at least two pathways, the dominant of which (70%) results from an intramolecular Diels-Alder reaction to tetracyclo[4.2.1.0. 0 ]nonene followed by a homo-1,5-hydrogen shift to give tricyclo[4.3.0.0 ]nona-4,7-diene followed by another homo-1,5-hydrogen shift as revealed by deuterium and carbon-13 labeling in separate experiments summarized in Scheme 10.22. ... 

Upon flow pyrolysis at 500°C, x6>-tetracyclo[4.3.0.0. 0 ]nonene gave a mixture of dihydroindenes in which the c/ -8,9-dihydro isomer was but a minor component (Scheme 10.24). ... 

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